I'm sure I'm misunderstanding something about ack's file/directory ignore defaults, but perhaps somebody could shed some light on this for me: mbuck$ grep logout -R app/views/ Binary file app/views/shared/._header.html.erb.bak.swp matches Binary file app/views/shared/._header.html.erb.swp matches app/views/shared/_header.html.erb.bak: <%= link_to logout_text, logout_path, { :title => logout_text, :class => 'login-menuitem' } %> mbuck$ ack logout app/views/ mbuck$ Whereas... mbuck$ ack -u logout app/views/ Binary file app/views/shared/._header.html.erb.bak.swp matches Binary file app/views/shared/._header.html.erb.swp matches app/views/shared/_header.html.erb.bak 98:<%= link_to logout_text, logout_path, { :title => logout_text, :class => 'login-menuitem' } %> Simply calling ack without options can't find the result within a .bak file, but calling with the --unrestricted option can find the result. As far as I can tell, though, ack does not ignore .bak files by default.